Foxborough — Big days around Gillette Stadium are usually reserved for December and January.

Playoff games or regular-season games with playoff implications, these are the days that allow the perpetually present Patriots to peek ahead on their calendars. But of course, times are changing in Foxboro.

Busy installing a new offense as they open a new era, the Pats are gearing up for a couple critical days this week. No, not games. Not even a preseason game.

Joint, padded practices with the Panthers on Tuesday and Wednesday.

"I think this will be our first test. Tomorrow will be our first big test,” Patriots left tackle Trent Brown said of Tuesday’s practice. “With Game 1 three weeks away, tomorrow will be a nice gauge to see where we are and see what we need to do before Week 1."

Pats wide receiver Kendrick Bourne agreed.

Bourne and Brown were two of the more than two dozen players who sat out last week’s preseason opener against the Giants, when the coaching staff opted to instead play rookies and backups. Historically, the Patriots have weighed player performances during joint practices just as heavily, if not heavier, than those in preseason games when roster-building. This week, the Pats’ offensive and defensive starters will be pitted against the Panthers’ top talent in 1-on-1 drills and team settings.

“It’s a good test. We played Carolina last year, it was a good game,” Bourne said, referencing the Pats’ 24-6 win in Charlotte. “I know they're going to come here with a lot of good energy.”

Before Monday’s practice, Pats coach Bill Belichick detailed the benefits of joint practices, which the team has been holding for roughly a decade.

“We'll see some different X's and O's, but also maybe techniques on the way guys pass-rush or route-running or things like that. And, I would say, less predictability of practice,” he said. "We kind of know what's on the other side of the ball and what we can and can't do. Some things we aren't going to see from the opposite side of the ball. With a new team, everything's kind of new.

“So it keeps you on your toes and forces more communication and more awareness. And we need that."

Patriots wide receivers coach Ross Douglas noted that the Panthers run a zone-heavy defensive scheme, a stark contrast from the blitz-happy Giants last week. The Giants primarily played man coverage as they blitzed on half of the Patriots’ passing plays over the final three quarters.

“They will play their man (coverage), but they’re bigger and faster and longer in the secondary,” Douglas said. “(Panthers safety) Jeremy Chinn is a big, longer guy, Donte’ Jackson and C.J. Henderson have some length and speed. So it’ll be a good challenge for us.”

Last season, Carolina’s defense ranked 15th by Football Outsiders’ opponent-and-situation-adjusted metric DVOA. Pro Bowl defensive end Brian Burns leads a strong front, while former top picks, including defensive tackle Derrick Brown, linebacker Shaq Thompson and cornerback Jaycee Horn, are scattered across the unit.

Practices will start at 9:30 a.m. on Tuesday and Wednesday, before the teams go head-to-head in a Friday night preseason game. Kickoff from Gillette Stadium is set for 7 p.m.